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The elevation is a complicated environmental factor that affects the availability of light, temperature, soil nutrients, and moisture, thereby affecting the mountain ecosystem. However, it is unclear how the C:N:P ecological stoichiometry of leaf, soil, and litter changes along the altitudinal gradient, especially in the karst ecosystem in Southwest China. This work investigated the soil organic carbon (SOC), total phosphorus (TP), and total nitrogen (TN) contents, and the corresponding stoichiometric ratios of Pseudotsuga sinensisleaf, litter, and soil at an elevation range of 2127–2302 m in the northwestern Guizhou Province of China. The results indicated that altitude significantly affected the nutrient contents and stoichiometric ratios of P. sinensisin leaf, soil, and litter. The mean contents of C, N, and P in the P. sinensisforests were 473.57, 14.49, and 1.97 mg·g−1for leaves; 422.35, 8.36, and 1.08 mg·g−1for litter; and 40.59, 2.44, and 1.04 mg·g−1for soil, respectively. The C, N, and P contents of soil and leaf increased significantly, whereas those in the litter decreased significantly with elevation. The average ratios of C:N, C:P, and N:P were 32.97, 244.60, and 7.42 for leaves; 51.38, 395.53, and 7.79 for litter; and 16.68, 38.84, and 2.34 for soil, respectively. The leaf C:N, N:P, and C:P ratios showed a linear decrease with an increase in altitude, whereas C:P and C:N ratios in the litter and N:P and C:P ratios in soil showed a linear increase with an increase in altitude. The resorption efficiency of both N and P of P. sinensisincreased remarkably with altitude. The mean resorption efficiency of P (43.84%) was higher than that of N (40.91%). Since the N:P ratio in leaves predicts limited nutrition for plant development, we hypothesized that the N element limited the development of P. sinensis. Besides, nutrient contents were markedly related to the ratios in P. sinensisleaves, litter, and soil. The results indicate that P. sinensishad developed a favorable strategy to adapt to the high altitude and cope with unfavorable soil nutrient conditions. The N element was mainly limited to the development of P. sinensis. The P. sinensishad developed a favorable strategy to adapt to the high altitude and cope with unfavorable soil nutrient conditions. These findings highlight the relationship between the C:N:P stoichiometric ratios and altitude in plants, soils, and litters in the karst forest ecosystem, and provide insight on the better management of the karst forest ecosystems in Southwest China.

The scalability and the efficiency of the OpenFOAM-based parallel viscoelastic solver are greatly restricted by MPI operations. In this work, we proposed a comprehensive strategy of the computation and communication overlap and the hybrid parallelization with MPI and OpenMP to optimize the parallel viscoelastic solver on HPC platforms. Critical simulations based upon 3D contraction benchmark flow show that the efficiency of the parallel viscoelastic solver could be considerably improved, and an extra speedup of 2.20 could be obtained with 8 threads upon 2 MPI processes.

According to the metal powder injection molding process, the main influence factors of injection molding billet density distribution (such as: injection velocity, injection temperature, injection pressure, etc) was analyzed and a multiple input & multiple output BP neural network model for injection molding was build up to predict the density distribution of the billet intelligently based on ANN and GA. In addition, in light of the requirements for the density distribution of the metal injection molding billet, the influence factors were controlled intelligently. Applying this model in the metal injecting process, the density distribution of billet was predicted according to the injection parameters and the injection parameters was optimized according to the required density distribution of the billet. As the result, the error was less than 5% between the prediction values and the actual values of the density distribution of billet. With the optimized injection parameters to the injection process, the density distribution of billet closed to the requirements was achieved.

Metal powders behave high strain rate, viscous effect and first hardening then softening deformation characteristics during the forming process of high velocity compaction. The characteristics of high strain rate and viscous effect are described by composite nonlinear viscoelastic body which consists of non-linear spring, linear spring and high strain rate Maxwell element. The deformation characteristics of first hardening then softening can be described by changing the degree of the term of nonlinear spring from greater than 1 to less than 1. Constitutive relation of metal powder in high velocity compaction is established. The degree of the term of nonlinear spring is considered as a function of strain. The function is approximated by linear, quadratic and cubic polynomial and the stress-strain curves are analyzed respectively. Analysis results indicate that the constitutive equation can describe the deformation characteristics of metal powder in high velocity compaction.